Upright graphene heterojunction and preparation method thereof, photoelectric detector and use method and application thereof

Abstract

The invention relates to a vertical graphene heterojunction and a preparation method thereof, a photoelectric detector and a use method and application thereof, and the method comprises the steps: placing a substrate in a quartz tube, and then carrying out the vacuum pumping; introducing protective gas into the quartz tube and heating the quartz tube to a set temperature; closing the protective gas and vacuumizing again; the method comprises the following steps: firstly, introducing methane into an ethanol solution, and then introducing methane gas containing ethanol steam into a quartz tube so as to grow upright graphene on the surface of a substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photoelectric detection, in particular to a vertical graphene heterojunction and a preparation method thereof, a photoelectric detector and a use method and application thereof. BACKGROUND

[0002] As an important part of modern photoelectric information technology, the main function of photoelectric detector is to convert optical signals into electrical signals efficiently, which is widely used in the fields of optical communication, laser radar, infrared imaging and quantum detection.

[0003] Among them, the graphene photoelectric detector mainly relies on the photovoltaic effect, photothermal electron effect and photoelectric thermal effect of photo-generated carriers to realize the conversion of optical-electrical signals. The main optimization method of graphene photoelectric detector is to increase the specific surface area and porosity of graphene, so as to enhance the light absorption of graphene. However, in the prior art, the means for improving the specific surface area and porosity of graphene are relatively limited, and the specific surface area and porosity of graphene are difficult to be significantly improved, so the light absorption capacity of graphene is temporarily in a bottleneck state. SUMMARY

[0004] Therefore, it is necessary to provide a vertical graphene heterojunction and a preparation method thereof, a photoelectric detector and a use method and application thereof to solve the problem of insufficient light absorption capacity of graphene.

[0005] A preparation method of a vertical graphene heterojunction, characterized in that it comprises:

[0006] placing the substrate in a quartz tube, and then vacuumizing;

[0007] introducing a protective gas into the quartz tube and heating to a set temperature;

[0008] turning off the protective gas and vacuumizing again;

[0009] firstly introducing methane into an ethanol solution, and then introducing methane gas containing ethanol vapor into the quartz tube to grow vertical graphene on the surface of the substrate.

[0010] In some embodiments, the set temperature is 850-950℃, the power of the radio frequency plasma source is 200-300W, and the growth time of the vertical graphene is 4-6h.

[0011] In some embodiments, the pressure in the quartz tube during the growth of the vertical graphene is 10-40Pa.

[0012] In some embodiments, the flow rate of methane introduced into the ethanol solution is 0.5-1.5sccm.

[0013] In some embodiments, the pressure in the quartz tube during the vertical graphene growth process is 15 Pa to 25 Pa.

[0014] A vertical graphene heterojunction is prepared by the preparation method.

[0015] A photodetector comprising a power supply and the vertical graphene heterojunction, wherein the vertical graphene on the substrate is connected to the positive electrode of the power supply, and the substrate is connected to the negative electrode of the power supply.

[0016] A method for using the photodetector, wherein the ambient pressure of the photodetector is controlled to be lower than 100 Pa when the photodetector detects light.

[0017] In some embodiments, the ambient pressure of the photodetector is controlled to be lower than 10 Pa when the photodetector detects light, so that the photodetector can detect light with a wavelength of 2200 nm.

[0018] A vertical graphene heterojunction preparation device, comprising a liquid tank, a gas tank, a radio frequency plasma source, a quartz tube and a vacuum pump.

[0019] The liquid tank is used to place ethanol, the input end of the liquid tank is used to connect a methane gas cylinder, the input end of the gas tank is used to connect a protective gas, and the output end of the liquid tank and the output end of the gas tank are connected in parallel to the gas inlet end of the quartz tube, the radio frequency plasma source is installed on the quartz tube, and the gas outlet end of the quartz tube is connected to the vacuum pump.

[0020] An application of the photodetector in signal coding.

[0021] The present application has the following advantages:

[0022] The present application provides a preparation method of a vertical graphene heterojunction, which uses methane and ethanol as carbon sources, and the vertical graphene prepared by the method has a special morphology of curled sheet layers.

[0023] The vertical graphene in the vertical graphene heterojunction has a natural nanoresonant cavity inside and has a high porosity. The morphology helps to improve the specific surface area and multiple scattering ability, thereby inducing light to reflect and scatter multiple times inside or near the surface of the vertical graphene, effectively prolonging the propagation path of light in the vertical graphene, enhancing the interaction strength between light and the vertical graphene, improving the light absorption efficiency, reducing the recombination probability of carriers, and effectively improving the photoelectric response performance of the device. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1a and Figure 1bI-V curves of the photoelectric detector in Example 2 of the present application under illumination of light at different wavelengths (light power is 0.4 W / cm 2 , and the test environment is normal pressure);

[0025] Figure 2 Frequency-dependent noise current curve of the photoelectric detector in Example 2 of the present application;

[0026] Figure 3 Nyquist plot of the photoelectric detector in Example 2 of the present application (the insert is an equivalent circuit model);

[0027] Figure 4 Stability test graph of the photoelectric detector in Example 2 of the present application;

[0028] Figure 5 Photoelectric current amplitude decay curve of the photoelectric detector in Example 2 of the present application under different switching frequencies;

[0029] Figure 6 Response curve of the photoelectric detector in Example 2 of the present application under different switching frequencies;

[0030] Figure 7 Photoelectric current rise and fall time test curve of the photoelectric detector in Example 2 of the present application;

[0031] Figure 8 Response curve of the photoelectric detector in Example 2 of the present application after being placed in a normal temperature and humidity environment for different times;

[0032] Figure 9a SEM image of the vertical graphene heterojunction in Example 1 of the present application;

[0033] Figure 9b SEM image of the vertical graphene heterojunction in Example 2 of the present application;

[0034] Figure 9c SEM image of the vertical graphene heterojunction in Example 3 of the present application;

[0035] Figure 10 AFM image of the vertical graphene heterojunction in Example 2 of the present application;

[0036] Figure 11 Normalized electric field distribution graph of the vertical graphene heterojunction in Example 2 of the present application;

[0037] Figure 12 Absorption spectrum of the vertical graphene heterojunction in Example 2 of the present application;

[0038] Figure 13 I-V curves of the photoelectric detector in Example 1-Example 4 of the present application under illumination of light at 1550 nm;

[0039] Figure 14 AFM images of the vertically standing graphene heterojunction in Examples 1 - 4 of the present invention (where a corresponds to Example 1, b corresponds to Example 2, c corresponds to Example 3, and d corresponds to Example 4);

[0040] Figure 15 SEM image of the vertically standing graphene heterojunction in the comparative example of the present invention;

[0041] Figure 16 I - V curves of the photodetector in Example 2 of the present invention under 1550 nm light illumination with different optical power densities (the test environment is 5 Pa);

[0042] Figure 17 Curves of the responsivity and specific detectivity changes corresponding to the photodetector in Example 2 of the present invention under 1550 nm light illumination with different optical power densities (the test environment is 5 Pa);

[0043] Figure 18 I - V curves of the photodetector in Example 2 of the present invention under 1850 nm and 2200 nm light illuminations (the optical power is 45 mW / cm 2 , and the test environment is 5 Pa);

[0044] Figure 19 I - V curves of the photodetector in Example 2 of the present invention at different temperatures (the optical power is 90 mW / cm 2 , and the test environment is 5 Pa);

[0045] Figure 20 Comparison table of the Unicode and ASCII codes corresponding to the Chinese characters "海", "纳", "百", and "川";

[0046] Figure 21 Information encryption output signal of the photodetector in Example 2 of the present invention under zero bias voltage;

[0047] Figure 22 Schematic diagram of the result of the device for preparing the vertically standing graphene heterojunction in Example 1 of the present invention;

[0048] Figure 23 Diagram of the dependence of the temperature and pressure inside the quartz tube obtained by simulation using the finite - difference time - domain method. Detailed implementation manners

[0049] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the concept of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0050] Embodiment 1

[0051] Referring to Figure 22 , the embodiment first provides a device for preparing a vertical graphene heterojunction, which specifically comprises a liquid tank 1, a gas tank 2, a radio frequency plasma source 3, a quartz tube 4 and a vacuum pump 5.

[0052] The liquid tank 1 is provided with liquid ethanol, and the input end of the liquid tank 1 is connected to a methane gas cylinder 6. The gas tank 2 has two input ends, one of which is connected to an argon gas cylinder 7 and the other of which is connected to a hydrogen gas cylinder 8. The output end of the liquid tank 1 and the output end of the gas tank 2 are connected in parallel to the gas inlet end of the quartz tube 4, and the gas outlet end of the quartz tube 4 is connected to the vacuum pump 5. The radio frequency plasma source 3 is installed on the quartz tube 4. The input end and the output end of the liquid tank 1 and the input end and the output end of the gas tank 2 are each provided with a corresponding valve.

[0053] The embodiment further provides a method for preparing a vertical graphene heterojunction, which comprises the following steps in sequence:

[0054] Step 101: Place the substrate in the quartz tube 4, and then vacuum the inside of the quartz tube 4 to below 1 Pa.

[0055] For example, in the embodiment, the substrate material is Si.

[0056] Step 102: Introduce a protective gas into the quartz tube 4 and heat it to a set temperature.

[0057] For example, in the embodiment, the protective gas comprises hydrogen and argon, which are provided by the argon gas cylinder 7 and the hydrogen gas cylinder 8 respectively. The flow rate of the argon is 10 sccm, the flow rate of the hydrogen is 1 sccm, and the set temperature is 900°C. In other embodiments, the set temperature can be set to between 850°C and 950°C.

[0058] Step 103: Turn off the protective gas and vacuum the inside of the quartz tube 4 again to below 1 Pa.

[0059] Step 104: First, introduce the methane gas in the methane gas cylinder 6 into the ethanol solution to generate bubbles and promote the evaporation of the ethanol, and then introduce the methane gas containing ethanol vapor into the quartz tube 4 to grow vertical graphene on the surface of the substrate.

[0060] In the embodiment, the flow rate of methane is 1 sccm, the power of the radio frequency plasma source 3 is 250 W during the growth of the vertical graphene, the pressure in the quartz tube 4 is maintained at 10 Pa, and the growth time of the vertical graphene is 5 h.

[0061] After the vertical graphene is prepared on the substrate, the vertical graphene heterojunction is obtained.

[0062] The embodiment further provides an optoelectronic detector, which comprises a power supply and the vertical graphene heterojunction. The vertical graphene is connected to the positive electrode of the power supply, and the substrate is connected to the negative electrode of the power supply.

[0063] Embodiment 2:

[0064] The embodiment differs from the embodiment 1 in that the pressure in the quartz tube 4 is maintained at 20 Pa in the step 104.

[0065] Embodiment 3:

[0066] The embodiment differs from the embodiment 1 in that the pressure in the quartz tube 4 is maintained at 30 Pa in the step 104.

[0067] Embodiment 4:

[0068] The embodiment differs from the embodiment 1 in that the pressure in the quartz tube 4 is maintained at 40 Pa in the step 104.

[0069] Comparative embodiment:

[0070] The comparative embodiment also provides a preparation method of a vertical graphene heterojunction, which comprises the following steps in sequence:

[0071] Step 101a: placing a silicon substrate into a quartz tube 4, and then vacuumizing the inside of the quartz tube 4 to below 1 Pa.

[0072] Step 102a: introducing hydrogen and argon into the quartz tube 4 and heating to 900 ℃. The flow rate of argon is 10 sccm, and the flow rate of hydrogen is 1 sccm.

[0073] Step 103a: closing the protective gas and vacuumizing the inside of the quartz tube 4 to below 1 Pa again.

[0074] Step 104a: heating ethanol to form ethanol vapor, introducing the ethanol vapor into the quartz tube 4, and growing vertical graphene on the surface of the substrate.

[0075] In the growth process of the vertical graphene of the comparative embodiment, the power of the radio frequency plasma is 250 W, the pressure in the quartz tube 4 is maintained at 20 Pa, and the growth time of the vertical graphene is 3 h.

[0076] Firstly, as shown in Figure 1a , the photoelectric detector in Example 2 has good response ability to excitation light with a wavelength of 440 nm-1550 nm under normal temperature and pressure test conditions. However, on the other hand, as the wavelength of the excitation light gradually increases from 440 nm, the photocurrent of the photoelectric detector gradually decreases. Further as shown in Figure 1b , under normal temperature and pressure test conditions, when the wavelength of the excitation light is 2200 nm, the photocurrent and dark current of the photoelectric detector are almost equal, in other words, the photoelectric detector at this time cannot detect 2200 nm light. It can be seen that under normal temperature and pressure test conditions, the detection range of the photoelectric detector in Example 2 is 440 nm-1550 nm.

[0077] As shown in Figure 2 , the noise current of the photoelectric detector in Example 2 is , the noise level is low, in other words, the signal-to-noise ratio is high. Thus it is proved that the photoelectric detector in Example 2 can realize high-precision detection of weak light signals.

[0078] As shown in Figure 3 , the photoelectric detector in Example 2 has a large charge transfer resistance, in other words, it has a strong trapping ability for photo-generated carriers, so it can suppress the recombination of electron-hole pairs and improve the separation efficiency of electron-hole pairs, thereby enhancing the light response performance of the device.

[0079] As shown in Figure 4 , under the conditions of 1550 nm light and zero bias voltage detection, the photocurrent of the photoelectric detector in Example 2 does not decrease significantly in 200 consecutive on-off cycles, proving the excellent cycle reliability of the photoelectric detector in the self-powered working mode.

[0080] As shown in Figure 5 , the -3 dB cutoff frequency of the photoelectric detector in Example 2 is as high as 1 kHz, proving that the photoelectric detector has a fast dynamic response ability and can efficiently modulate optical signals. Further as shown in Figure 6 , under the conditions of -3 V bias voltage and 1550 nm light, the normalized photocurrent when the switching frequency is 250 Hz, the normalized photocurrent when the switching frequency is 500 Hz, and the normalized photocurrent when the switching frequency is 1000 Hz are all very stable.

[0081] As shown in Figure 7 , the rise time and fall time of the photocurrent of the photoelectric detector in Example 2 are 130 μs and 154 μs, respectively. Short rise time and fall time indicate that the photoelectric detector can quickly capture and convert optical signals into electrical signals, which is conducive to meeting the application requirements of high-speed optical communication and real-time monitoring.

[0082] As shown in Figure 8 , the photocurrent of the photodetector in Example 2 did not obviously attenuate after being placed for 1 month, 2 months, 3 months and 4 months under normal temperature and humidity conditions, which proves that the photodetector has good physical stability and optical inertness.

[0083] Based on the above test results, it is fully proved that the photodetector and the vertical graphene heterojunction in Example 2 have excellent photoelectric detection performance. In addition, the photodetectors in Example 1, Example 3 and Example 4 also have excellent photoelectric detection performance. Therefore, the vertical graphene in Example 1-Example 4 has a special morphology.

[0084] Specifically as shown in Figures 9a-9c and Figure 10 , the vertical graphene in Example 1-Example 3 has a curled sheet structure, and there is a natural nanoresonant cavity inside, which helps to improve the specific surface area and multiple scattering ability. As shown in Figure 11 , when light is incident on the surface of the vertical graphene, the curled sheet structure and the nanoresonant cavity of the vertical graphene can induce multiple reflections and scattering of light inside or near the surface of the vertical graphene, thereby effectively prolonging the propagation path of light in the vertical graphene, enhancing the interaction strength between light and the vertical graphene. The light localization effect produced thereby significantly improves the light absorption efficiency, helps to efficiently excite photogenerated carriers in the local enhanced electric field region, and promotes the separation and transport of the carriers, thereby effectively improving the photoelectric response performance of the device. As shown in Figure 12 , the light absorption rate of the photodetector in Example 2 at 1550 nm wavelength is as high as 89%.

[0085] Further referring to Figure 13 , as the pressure environment during the growth of the vertical graphene rises from 10 Pa to 40 Pa, the photocurrent of the photodetector first increases and then decreases, and reaches a maximum value at 20 Pa. Under the conditions of a power density of 0.4 W / cm 2 , and an effective light irradiation area of 1.256 x 10 -5 cm 2 , the responsivity and specific detectivity data of Example 1-Example 3 are shown in Table 1.

[0086] Table 1

[0087] Based on the data in Table 1, it can be proved that for the vertical graphene of the present application, the pressure environment during the growth process must have a significant impact on the final morphology, and when the pressure is 20 Pa, the morphology of the vertical graphene is most conducive to photoelectric detection.

[0088] In particular reference is made to Figures 9a-9c and Figure 14 The height of the standing graphene in Example 1 is 0.6 μm, the porosity is 68%, the height of the standing graphene in Example 2 is 4.8 μm, the porosity is 73%, the height of the standing graphene in Example 3 is 1.3 μm, the porosity is 71%, and the porosity of the standing graphene in Example 4 is 70%, which proves that for the standing graphene of the present application, the pressure environment during the growth process has a significant influence on the final height and porosity of the standing graphene, which in turn causes differences in the photoresponsivity and specific detectivity of the photodetector. At the same time, the increase in the height and porosity of the standing graphene also plays an important role in the increase in the final photoresponsivity and specific detectivity.

[0089] The unique morphological characteristics of the standing graphene in the present application are mainly caused by the following factors:

[0090] 1. The carbon source during the growth of the standing graphene is selected as both methane and ethanol, and the content of ethanol is greater than that of methane.

[0091] Among them, if only methane is introduced to maintain the pressure of 20 Pa inside the quartz tube 4, the flow rate of methane needs to be as high as 10 sccm, which is quite different from the 1 sccm flow rate of methane in Examples 1-4. This proves that the carbon source in the growth process of the standing graphene of the present application mainly comes from ethanol, and methane plays a supplementary role in the carbon source. On the other hand, as shown in Figure 15 , in the case of using only ethanol as the carbon source, the standing graphene not only grows slowly, but also has a height of only 400 nm (much lower than 4.8 μm in Example 2), and the pore size is also relatively small. This proves that the joint use of methane and ethanol as the carbon source plays a very important role in forming the unique morphology of the standing graphene of the present application.

[0092] 2. In the plasma environment of PECVD, the activation energy barrier required for the bond breaking of precursor molecules can be reduced, so that ethanol and methane molecules can be cracked under the action of high-energy electron bombardment to generate a large amount of active carbon radicals and a small amount of H and OH radicals. Under low pressure conditions, as the plasma density and electron temperature increase, the collision frequency of electrons with ethanol and methane molecules increases, further reducing the activation energy of ethanol and methane in the cracking process, increasing the concentration of carbon radicals, and at the same time, H radicals continuously etch the surface defect area of the graphene thin layer, inhibiting the accumulation of thick films. It is worth noting that if the pressure is too low, it means that the carbon source is insufficient, which will also affect the growth of the standing graphene.

[0093] 3. As shown in Figure 23As shown, analysis using the finite-difference time-domain method revealed that the low-pressure environment enhances the thermal accumulation effect inside the quartz tube 4, increasing the local temperature on the substrate surface. This effectively reduces the surface diffusion activation energy for carbon free radical migration and directional nucleation on the substrate surface, promoting the directional nucleation of carbon atoms in regions with lower energy barriers, such as defects and steps. Furthermore, combined with the non-equilibrium plasma-assisted CVD growth mode under PECVD conditions, the vertical growth rate of upright graphene is much greater than the surface diffusion rate, achieving diffusion-limited conditions. The active carbon source rapidly deposits locally on the substrate, causing the graphene sheets to curl, overlap, and self-organize within microscale regions, forming the unique morphology of this application.

[0094] Further as Figure 16 As shown, under a 5Pa test environment, the photocurrent of the photodetector in Example 2 increases with the increase of excitation light power density. Furthermore, under the same excitation light power density, the photocurrent of the photodetector under a 5Pa test environment is significantly greater than the photocurrent under a normal pressure test environment. Figure 17 As shown, the test environment is 5Pa and the excitation light power density is... Effective light area Under the conditions, the responsivity of the photodetector in Example 2 The detection rates were 82 A / W and 82 A / W, respectively. In contrast, the ambient pressure testing environment and the excitation light power density... (Minimum power with light response), effective illumination area Under these conditions, the responsivity and specific detectivity of the photodetector in Example 2 are only 28 A / W and A significant decline occurred.

[0095] The improvement in photocurrent, responsivity, and detectivity of the device by reducing the atmospheric pressure of the detection environment is mainly attributed to the fact that the low-pressure environment reduces the adsorption of air molecules and water vapor on the graphene surface, decreasing the number of recombination centers on the graphene surface. This suppresses nonradiative recombination of photogenerated carriers, improves carrier lifetime and collection efficiency, and allows more photogenerated carriers to participate in the conduction process. Furthermore, the reduced number of interface defect states and adsorbed states under low pressure significantly reduces carrier recombination losses, thereby effectively improving the device's photoelectric conversion efficiency and weak signal detection capability.

[0096] like Figure 18As shown, the spectral response range of the photodetector in Example 2 is extended from 1550 nm (normal pressure test environment) to 2200 nm (5 Pa test environment) under the 5 Pa test environment. This is also due to the low-pressure environment reducing the surface trap state density of the vertical graphene, reducing the recombination probability of low-energy carriers on the vertical graphene surface generated by long-wave photon excitation, and the photodetector can respond to photon excitation of longer wavelengths (lower energy), thereby expanding the response wavelength band of the detector.

[0097] By reducing the air pressure of the test environment from normal pressure to 5 Pa, the performance of the photodetector in Example 2 is significantly improved, which reflects the larger specific surface area of the vertical graphene in Example 2 and the stronger adsorption of impurities in the air.

[0098] As shown in Figure 19 , as the temperature rises, the thermal excitation of carriers in the vertical graphene is enhanced, the mobility is improved, and the recombination probability is reduced, thereby improving the collection efficiency of photo-generated carriers, and further increasing the photocurrent.

[0099] Four Chinese characters "sea", "Nai", "hundred", and "river" are selected as encryption information carriers, and the corresponding Unicode encoding and 8-bit ASCII code are as shown in Figure 20 . The encoded binary signal is loaded on the modulation laser through the signal generator to realize the modulation of the laser pulse, where "1" represents the laser on and "0" represents the laser off. Under the modulation of 1550 nm laser, the self-driven photodetector of the vertical graphene heterojunction in Example 2 can generate photo-generated carriers by relying on incident light excitation, and realize efficient carrier separation and rapid signal output by the built-in electric field driving at the heterojunction interface. As shown in Figure 21 , the photodetector in Example 2 can respond in real time and accurately reproduce the binary signal encoded by the modulation laser, and through the semiconductor analyzer, the optical signal is converted into the corresponding electrical signal to complete the information encryption and decoding transmission of complex binary optical signals. Relying on its excellent photoelectric conversion capability and built-in electric field assisted separation mechanism, the device realizes high-sensitivity, stable, and passive information encryption transmission.

[0100] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0101] The above embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of protection of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing an upright graphene heterostructure, characterized in that, include: The substrate was placed in a quartz tube, and then a vacuum was drawn. A protective gas is introduced into the quartz tube and heated to the set temperature; Turn off the protective gas and evacuate again; First, methane is passed into an ethanol solution, and then methane gas containing ethanol vapor is passed into a quartz tube to grow vertical graphene on the substrate surface.

2. The method for preparing upright graphene heterostructures according to claim 1, characterized in that, The set temperature is 850℃-950℃, the power of the radio frequency plasma source is 200W-300W, and the growth time of the upright graphene is 4h-6h.

3. The method for preparing upright graphene heterostructures according to claim 1, characterized in that, During the growth of upright graphene, the pressure inside the quartz tube is 10 Pa to 40 Pa.

4. The method for preparing upright graphene heterostructures according to claim 3, characterized in that, The flow rate of methane into the ethanol solution is 0.5 sccm-1.5 sccm.

5. The method for preparing upright graphene heterostructures according to claim 3, characterized in that, During the growth of upright graphene, the pressure inside the quartz tube is 15 Pa to 25 Pa.

6. An upright graphene heterostructure, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

7. A photodetector, characterized in that, It includes a power source and an upright graphene heterojunction as described in claim 6, wherein the upright graphene on the substrate is connected to the positive terminal of the power source, and the substrate is connected to the negative terminal of the power source.

8. A method of using the photodetector as described in claim 7, characterized in that, When the photodetector performs light detection, the ambient pressure of the photodetector is controlled to be below 100 Pa.

9. The method of using the photodetector according to claim 8, characterized in that, When the photodetector performs light detection, the ambient pressure of the photodetector is controlled to be lower than 10 Pa to allow the photodetector to detect light at 2200 nm.

10. An apparatus for preparing upright graphene heterostructures, characterized in that, It includes a liquid tank (1), a gas tank (2), a radio frequency plasma source (3), a quartz tube (4), and a vacuum pump (5); The liquid tank (1) is used to hold ethanol. The input end of the liquid tank (1) is used to connect to the methane cylinder (6). The input end of the gas tank (2) is used to connect to the protective gas. The output ends of the liquid tank (1) and the gas tank (2) are connected in parallel to the gas inlet of the quartz tube (4). The radio frequency plasma source (3) is installed on the quartz tube (4). The gas outlet of the quartz tube (4) is connected to the vacuum pump (5).

11. An application of the photodetector as described in claim 7 in signal encoding.

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